20505865 has 16 divisors (see below), whose sum is σ = 25505280. Its totient is φ = 15816640.

The previous prime is 20505853. The next prime is 20505869. The reversal of 20505865 is 56850502.

It is not a de Polignac number, because 20505865 - 2¹⁵ = 20473097 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20505869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16071 + ... + 17299.

It is an arithmetic number, because the mean of its divisors is an integer number (1594080).

Almost surely, 2^20505865 is an apocalyptic number.

It is an amenable number.

20505865 is a deficient number, since it is larger than the sum of its proper divisors (4999415).

20505865 is a wasteful number, since it uses less digits than its factorization.

20505865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1352.

The product of its (nonzero) digits is 12000, while the sum is 31.

The square root of 20505865 is about 4528.3402036508. The cubic root of 20505865 is about 273.7112814724.

The spelling of 20505865 in words is "twenty million, five hundred five thousand, eight hundred sixty-five".